Democrats’ hopes of holding on to their Senate seat in Florida appear to be looking up, with a new Washington Post poll showing Sen. Bill Nelson (D) holding a 14-point lead on Rep. Connie Mack (R) among likely voters, 54 percent to 40 percent.

Nelson, who also leads by 18 points among registered voters, holds a strong edge among basically all the key swing demographics, including among independents (55-37), moderates (65-25) and in the Tampa Bay (56-41) and Orlando (49-43) areas along the crucial Interstate-4 corridor.

Nelson also wins more Republicans (15 percent) and voters who chose Sen. John McCain (R-Ariz.) in the 2008 presidential race (18 percent) than Mack wins among Democrats (4 percent) and 2008 supporters of President Obama (11 percent).

The poll is the latest showing of a key Senate race that is trending toward Democrats.

While Mack was able to close the gap during the summer and even led in some polls, four polls this month have shown Nelson building a double-digit lead: an automated SurveyUSA poll, an NBC News/Marist College poll, a Fox News poll and, last week, a Mason-Dixon poll that had Nelson leading 48 percent to 40 percent.

Democrats have also made gains in close races in Massachusetts, Virginia and Wisconsin. And in another Washington Post poll today, Democrats were asserting a double-digit lead in Ohio.

But whatever shift has happened in the national electoral counting, the poll of Florida suggests that the shift in that state is more about the two candidates. Nelson has strong numbers at 55 percent favorable and 33 percent unfavorable, but Mack is underwater at 41 percent favorable and 45 percent unfavorable.

Nelson, like Democratic Sen. Sherrod Brown of Ohio, has long been considered a second-tier GOP target this cycle. Though Florida is a swing state, Republicans continue to have problems recruiting strong candidates against the two-term senator.

Here's the release from PPP :

PPP's newest Florida Senate poll finds Bill Nelson continuing to expand his lead. He's at 46% to 37% for Connie Mack IV. Three weeks ago Nelson led by 7 points and in early July he had been ahead by only 2.

Nelson's still not popular. Only 34% of voters approve of him to 41% who disapprove. But he lucked out with an extremely weak opponent.

Only 30% of voters have a favorable opinion of Mack to 44% with a negative one. Mack's numbers are a particularly dreadful 22/53 spread with independents, and he trails Nelson by 22 points with them at 48-26.The most striking finding in the poll is that Nelson leads Mack 44-41 with white voters.

If a Democrat can win white voters in Florida they're headed for a blowout victory overall, and increasingly that appears to be the case in this race-Mitt Romney didn't get much of a bounce out of the Republican convention in Florida, but Marco Rubio sure has. His approval breakdown this month is 52/32, the best we've found for him since he took office. He's on solid 50/33 ground with independents and has a higher than normal 26% of Democrats who approve of him.

Rubio's approval numbers were pretty middling for the last year and a half but he's seen a noticeable improvement since the convention.-38% of Florida voters approve of Rick Scott this month to 48% who disapprove. His numbers, although still bad, continue to be better than they've been for most of his term. Scott trails a generic Democratic opponent for reelection by a 48/42 margin.

One specific person who seems like he could be the Democratic candidate for Governor in 2014 is Charlie Crist. He leads Scott 48-43 in a hypothetical contest. Crist is not an overwhelmingly popular figure in Florida anymore though. 39% of voters have a favorable opinion of him to 43% with a negative one.

His numbers with Democrats (up from 44/33 to 55/22) and Republicans (down from 24/60 to 19/69) have headed in opposite directions in the three weeks since he appeared at the Democratic convention. 48% of voters think he should complete the switch and become a Democrat to 21% who think he should not and that sentiment is held among Democrats (61/11) and Republicans (40/33) alike.